Diffuse sky radiation is solar radiation reaching the Earth's surface after having been scattered from the direct solar beam by molecules or suspensoids in the atmosphere. It is also called skylight, diffuse skylight, or sky radiation and is the reason for changes in the colour of the sky. Of the total light removed from the direct solar beam by scattering in the atmosphere (approximately 25% of the incident radiation when the sun is high in the sky, depending on the amount of dust and haze in the atmosphere), about two-thirds ultimately reaches the earth as diffuse sky radiation.
The important processes in the atmosphere (Rayleigh scattering and Mie scattering) are elastic processes, by which light can be deviated from its path without being absorbed and with no change in wavelength.
A twig is a small thin terminal branch of a woody plant. Twigs are critically important in identification of trees, shrubs and vines, especially in wintertime. The buds on the twig are an important diagnostic characteristic, as are the abscission scars where the leaves have fallen away. The color, texture, and patterning of the twig bark are also important, in addition to the thickness and nature of any pith of the twig.
There are two types of twig, vegetative twigs and fruiting spurs. Fruiting spurs are specialized twigs that generally branch off the sides of branches and leading twigs, and are stubby and slow-growing, with many annular ring markings from seasons past. The age and rate of growth of a twig can be determined by counting the winter terminal bud scale scars, or annular ring marking, down the length of the twig. Are also these are as the many resources for utility or useful to others.